Warn about disk pressure condition

If the node's disk usage passes a relatively low threshold (85%?), kubernetes considers this a state of disk pressure and will start evicting pods, which should be avoided at all times, especially because we typically don't have a second node to move pods to.

It would be good to

  • Make a note of this in the docs to warn people and advise them to keep enough spare disk space.
  • Maybe create a prometheus rule to warn when disk usage gets close to the threshold, so you get an early warning.
Edited by Arie Peterson
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